1. Field of the Invention
The present invention generally relates to a method and an apparatus for mounting electronic components on a printed circuit board. More specifically, the present invention is directed to a technique capable of shortening so-called "mounting tact time" per one electronic component.
2. Description of the Related Art
Electronic components are mounted on printed circuit boards by automatic machines, for instance, components mounting apparatuses for using so-termed "mounting type electronic components". One of these automatic components mounting apparatuses is described in, e.g., Japanese Laid-open Patent Application No. 5-192824.
This components mounting apparatus is equipped with the turn table 13 and a plurality of mounting heads 15. The turn table 13 is hung on the supporting base 28 and is intermittently and rotatably provided in such a manner that the rotation shaft is extended along the vertical direction. These mounting heads 15 are arranged on the outer peripheral portion of this turn table 13 along the peripheral direction. One of positions where the mounting head 15 is stopped corresponds to the absorption station. At this absorption station, the components supplying apparatus 8 for supplying the chip components 5 is provided. On the other hand, another position located opposite to the turn table 13 of the absorption station corresponds to the mounting station. The board 6 movably supported along the X-Y direction is mounted on the lower portion of the mounting head 15 positioned at this mounting station.
A plurality of components supplying apparatuses 8 are arranged within a preselected range containing a portion of the position corresponding to the absorption station of the turn table 13. A designated components supplying apparatus 8 is transported to the position corresponding to the absorption station.
One mounting head 15 absorbs the chip component 5 supplied from the components supplying apparatus 8 in the absorption station. Then, the turn table 13 is intermittently rotated by one pitch. The next mounting head 15 is located at the absorption station, and then absorbs the chip component 5 similar to the above-described mounting head 15. Then, the turn table 13 is again intermittently rotated. Thus, the chip component 5 is absorbed by the mounting head 15 located at the absorption station in this manner.
Then, the mounting head 15 which has absorbed the chip component 5 is transported to the mounting station by rotating the turn table 13. At this mounting station, the mounting head 15 descends to mount the chip component 5 on the board 6.
Prior to mounting of the chip component 5, the board 6 is moved by the X-Y table 3, so that this designated component mounting place is positioned in correspondence with the mounting station.
The above-described absorbing and mounting operations of the chip components 5 are carried out in accordance with a previously designated sequence. In other words, one components supplying apparatus designated in accordance with the above-described sequence among the components supplying apparatuses 8 is transported to the position corresponding to the absorption station. After this designated chip component 5 has been absorbed by the mounting head 15, this chip component 5 is transported by the turn table 13 to the mounting station. At the same time, the board 6 is transported by the X-Y table 3, and thus a predetermined position where this chip component 5 is mounted corresponds to the mounting station, so that the mounting head 15 descends so as to mount the designated chip component 5 on the board 6.
To shorten the components mounting tact time in such a conventional components mounting apparatus, while the respective mechanical elements (components supplying apparatuses, turn table, mounting head, etc.) are operated at high speed, the arranging sequence of these components supplying apparatuses 8 and also the transporting sequence (transporting sequence to mounting position) of the X-Y table 3 must be optimized. The cooperation between the respective mechanical elements and other mechanical elements must be optimized to thereby shorten the work waiting time. As a consequence, the absorbing sequence and/or the mounting sequence of the components by the mounting head 15 must be effectively set.
For instance, the transporting sequence of the X-Y table 3 is determined in this order, namely such a predetermined mounting position located near the edge of preselected mounting positions on the board 6. This way causes the transporting sequence to be optimized only if the transport time of the X-Y table 3 is considered. However, when this transporting sequence is designed on the basis of the arranging order of the components supplying apparatuses 8, since there are many possibilities that a plurality of same sorts of components are mounted on the board 6, the components supplying apparatuses 8 must be transported in the reciprocation motion every time the same sort of components are mounted. Therefore, the above-described transporting sequence of the X-Y table 3 is not always the optimum transporting sequence for the components supplying apparatus 8. Accordingly, the overall mounting tact time could not be shortened.
Also, in such a case that the components supplying apparatuses 8 are arranged in accordance with a certain sequence, for example, in a higher use-frequency order, and the transporting sequence of the X-Y table 3 is designed based on this arranging sequence, this transporting sequence of the X-Y table 3 does not always correspond to the optimum transporting sequence with respect to the X-Y table (3). In other words, this designed transporting sequence is not substantially equal to the optimum transporting sequence. As a result, there are many problems that when such a design is made on the basis of any one of the arranging sequence of the components supplying apparatuses 8 and the transporting sequence of the X-Y table 3, the other sequence would become unsuitable. It is practically difficult to determine either the optimum sequences or the sequences close to these optimum sequences for both cases.
This is caused because the transportation of the components as the operation switches between absorbing of the components and mounting the components is performed by rotating the turn table 13 along one direction, and thus such a fact that the degree of freedom in designing of these sequences is low.
Eventually, since the transportation of the components as the operations switches between absorbing of the components and mounting of the components is carried out by rotating the turn table 13 along one direction, there are limitations in designing and optimizing the arranging sequence and the transporting sequence. Accordingly, the components mounting tact time could not be shortened.